An airplane is provided with plural wheels under the body or wings for taking off, landing and parking. The wheels support the body so that the airplane can move on the runway. When taking off, by the thrust power of the engine, the airplane runs on the runway through the wheels with the speed gradually increasing, and soon the wheels are detached from the ground of the runway by the dynamic lift that the wings receive to lift the body. When the airplane lifts to a sufficient height, the wheels are enclosed within the body.
On the contrary, when landing, the wheels are drawn out with sufficient time before landing, and the airplane gradually reduces the altitude. After the wheels contact the runway, the airplane runs on the runway through the wheels which support the weight of the body, the speed of the airplane is gradually reduced, and the airplane comes to a halt.
Hereof, ordinary wheels of the airplane are rotatably supported by axles and not equipped with a driving apparatus. Accordingly, before landing, the wheels, which will support the weight of the body, are not rotating and are stagnant. On the contrary, at the instance when the airplane lands, bottom surfaces of the wheels receive a strong shock of force in the tangential direction from the front surface of the runway by the frictions between the tire of the wheels and the runway, and thus driving the wheels. Namely, the wheels of the airplane receive so much shock force that the number of revolutions of the wheel changes from zero to the value corresponding to the flight speed at the moment of landing. The flight speed at the landing of a passenger plane with jet engine is about 200˜300 km/hour. The shock force, which brings the change of the revolution number of landing, erodes the tire of the wheel, and surface portion of the tire is stripped by the sliding resistance between the runway and the tire resulting in the generation of white smoke at landing. Further the remnant or residue of the tire sticks to form a layer on the landing point of the runway. The stuck remnant or residue layer must be removed periodically by the stripping apparatus from the runway. Hence the maintenance of the runway is very troublesome.
Japanese Patent Openings H5-178290, H8-254176, and 2001-146199 disclose wheel driving devices which drive the wheel in a direction same as the direction of the wheel after landing by utilizing the relative atmospheric air flow, to which the airplane receives before landing.
The device disclosed in the Japanese Patent Opening H5-178290 is to provide plural, for example, six, projections at the predetermined pitch on the side surface of the tire. This device makes the manufacture of the tire of airplane very difficult and increases the cost of the tire. Further, as the projections project in the axial direction of the tire, the normal torque by the projection at the lower side of the tire and the reverse torque by the projection at the upper side of the tire cancels each other. Accordingly, sufficient torque cannot be brought to the tire.
In the Japanese Patent Opening H8-254176 and Japanese Patent Opening 2001-146199, the grooves formed on the tires of the wheels of airplane are disclosed. That is, fins are formed in the longitudinal groove of the tire, or the shape of the groove on the tread of the tire is devised to form a wedge, causing the revolution of the wheel by the relative atmospheric air flow brought by the flight. But due to the structure of the grooves of the tire, sufficient thickness of the tread of the tire is required, resulting in the increase of the weight of the airplane. Further, when the tire is worn, the structures of the grooves generating the torque by the relative atmospheric air flow are also worn down or broken down, causing a failure of the revolution of the wheel. Further, the cost of the tire increases because the tire requires the groove of special structure.
PATENT REFERENCE No. 1: Japanese Patent Opening H5-178290
PATENT REFERENCE No. 2: Japanese Patent Opening H8-254176
PATENT REFERENCE No. 3: Japanese Patent Opening 2001-146199